This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 9 |
| 4 | 44 |
| 5 | 290 |
| 6 | 2154 |
| 7 | 19026 |
| 8 | 186752 |
| 9 | 2070792 |
| 10 | 25119720 |
| 11 | 334960560 |
| 12 | 4824346152 |
| 13 | 75100568088 |
| 14 | 1250180063664 |
| 15 | 22235660291880 |
| 16 | 419595248663040 |
| 17 | 8388866239417920 |
| 18 | 176823515257447104 |
| 19 | 3923498370610292544 |